Manufacture of hollow steel or iron bars, tubes, shafts, rock drills, and the like



-May 2.2, 3923. a,455,%5 R. A. DFOR MANUFACTURE OF HOLLOW STEEL OR I N BARS BBS SHAFTS ROCK DRILLS AND THE LIKE Filed Dec. 1, 1922 Patented May 22, E323 stares,

intent magma nnernarn a. nnnronn, or snnrrrnnn, nnenann.

MANUFACTURE HOLLOIV STEEL R IRON BARS, TUBES, SHAPES, ROCK DRILLS,

, AND THE LIKE.

Application filed December 1, 1922. Serial No. 604:,432.

To all whom it may concern: Be it known that REGINALD Asmara BED- FORD, subject of the King ofGreat Britain is a specification, reference being had to the accompanying drawing. This invention relates to the manufacture of hollow steel or iron bars, tubes, shafts, rock-drills, and other longitudinally apertured articles by rolling or forging a tubular billet, bloom or in 0t.

The invention is dlrected to that known processor method of manufacture wherein a billet, bloom or ingot is formed, throughout its length, with a hole into which is 29 inserted a metallic bar constituting a core, whereupon the heated mass is worked to the required dimensions, and, when cooled, the core is mechanically withdrawn. The core, in the course of withdrawal, is 2 apt to break within the worked or finished mass in the form of a bar or other article, and the extraction of the portion remaining is fraught with difliculty. To obviate this,

defect. it has been proposed to make the 0 core in two lengths, and withdraw each,

length separately at the corresponding end of the mass.

In practice it is found that the double core, while withdrawing more or less satis- 3 factorily has a great d1sadvantage,viz, in the process of rolling o'r forging the two cores get separated thus causing a portion of the middle of the finished hollow bar to be blind or without a hole of proper section 4 and in some cases no hole whatever but merelya fissure.

The object of this invention is to efi'ect the withdrawal of the copper or similar metal I core with facility by intentionally fracturing it within the mass. To this end the invention consists in weakening the structure of the core at a place intermediate of its ends, preferably at or about the middle, previous to inserting it in the billet,

5a bloom or'ingot. This is efiected by removing the constituent material and replacing it by a filling of the same, or a dissimilar, material. Thusthe cohesion of the core is effected by the filling, which, however, preserves the contour' of the corethereby ensuring it'performing its function.

Therefore, the core, when it is subjected to the tensile stress requisite for withdrawal, will break and part into two portions which are extracted separately at the appropriate ends of the mass in its worked or finished form. The advantage accrues in the fact that the core is ensured of breaking at a position in the finished bar where the hole is of the smallest area. It is found in practice that in the production of a long bar there is a slight variation in the diameter of the hole,

.it being smaller in the centre of the bar with a'gradual increase in diameter towards the ends of the bar. When using a solid core, should the core break say two-thirds up the bar, it is necessary to draw the core through a hole with a smaller diameter, resulting in the core breaking, and leaving a portion of core tightly wedged towards the centre of the bar, hence the advantage of purposely weakening the core near the middle.

The weakening may becreated by-nicking, sawing, or boring, or any combination thereof, carried out transversely and in any usual way. The nick or sawgate may ex tend through one-third or thereabouts of the thickness of the core, whilst the hole or bore may be continuous. The number, type, size and the spaced relation of these weakening expedients are determined by the material of which the core is constituted, and the dimensions of the core. A filling is inserted in the nick, sawgate, or hole, such consisting of the same material as the core, or a different material, and it may be run into the gap or space in a molten state and allowed to cool, or it may be in the form of a solid plug. In either case, the structural continuity of the core is interrupted and designed liability to fracture is presented under the application of the pulling power in the withdrawing operation.

The filling may be of a character that may be melted out, as is well known in the art, prior to the withdrawing operation; for example, it may consist of copper or a copper alloy.

As'an example of the manner in which such a core may be formed, there is disclosed in the accompanying drawings certain typical forms thereof. In these drawings-- Fig. 1 is a side elevation of one form of the core with the billet shown in section.

Fig. 2 is a side elevation of a second'form of such core.

In the form shown in Fig. 1, it will be observed that there is provided a core 10 having saw cut or nick 11 formed therein which is filled with a suitable filling 12.

In Fig. 2, there is disclosed a hollow core 13 having a transverse opening 14 at its central portion filled with a suitable filling 15. It is to be observed that both of these cores are centrally weakened, and that such a billet as B may be assembled on either one.

Claims:

1. That process of formin tubes from hollow billets which consists 1n placing the billet on a mandrel of the required interior diameter of the tube and having a weakened central portion, forming the billet into an elongated cylinder 011 83.16. mandrel, applying tensile stress to the mandrel at the opposite ends thereof to fracture the weakened portion, and withdrawing the broken mandrel sections from opposite ends of the formed billet.

2. As a new article of manufacture for use as a core to a tubular billet, bloom or ingot in the process or method of manufacture referred to, a bar having aca-vity therein for the purpose of weakening it and a solid filling piece inserted in said cavity for maintaining the contour of the core.

In witness whereof I have hereunto set may hand in presence of two witnesses.

REGINALD A. nnnronn.

Witnesses:

ENson D. DRURY, DENNIS. S. DRURY. 

